Recently, an LTE-advanced (LTE-A) communication system, a high speed communication system capable of supporting wider band as compared to the existing LTE system, has newly appeared.
Transmission mode 9 (TM-9) and Transmission mode 10 (TM-10), one of functions of the LTE-A communication system, support channel state information reference signal (CSI-RS) and demodulation reference signal (DMRS), instead of cell specific reference signal (CRS) supported in TM-3 and TM-4 in the existing LTE system for channel state estimation.
In the LTE-A communication system, the CSI-RS and the DMRS supported in TM-9 and TM-10 are utilized, such that the same physical cell identifier (PCI) may be assigned to two or more adjacent cells to form one virtual cell. Thus, interference at a cell edge is improved, and a terminal may move without inter-cell handover in one virtual cell.
In the LTE-A communication system, the same physical cell identifier (PCI) is assigned to two or more cells to form one virtual cell. Therefore, regarding a terminal located in an overlapped area in which cells (for example, C2 and C3) are overlapped with each other, C2 and C3 each allocate the same radio resource to the terminal, such that the terminal is provided with the same communication service through C2 and C3 at the same time.
Meanwhile, in the LTE-A communication system, regarding terminals located in a central area of each of the cells C2 and C3, not the overlapped area, each of the cells C2 and C3 allocates separate radio resource to the terminals as in the related art, such that the terminals are provided with the communication service through C2 and C3, respectively.
However, when two or more cells are managed as one virtual cell as described above, interference at a cell edge may be improved but the effect of enhancing the operation efficiency of radio resources resulting from frequency reuse may be deteriorated, that is, a tradeoff occurs.
In particular, in a heterogeneous network environment in which cell having different sizes, that is macro cells and small cells coexist, since the small cells are newly installed and placed irregularly as needed, severe tradeoff may occur depending on environmental factors (e.g. the number of small cells, a distance between cells, an amount of traffic, etc.) of the small cells when the virtual cell is managed with respect to the small cells.
Accordingly, the present invention is to harmoniously satisfy the effects of improving intercell interference and enhancing the operation efficiency of radio resources in managing virtual cells, particularly in managing virtual cells in a heterogeneous network environment.